Proceedings of 

 the United States 

 National Museum 



SMITHSONIAN INSTITUTION • WASHINGTON, D.C. 



Volume 112 1960 Numl.er 3447 



THE FAIRY SHRIMP BRANCHINECTA CAMPESTRIS 



FROM NORTHWESTERN UNITED STATES 



(CRUSTACEA: PHYLLOPODA) 



By James E. Lynch ' 



The following description of a fairy shrimp belonging to the genus 

 Branchinecta is the result of the study of 33 collections from 9 diff- 

 erent localities, made between 1937 and 1958. The data contained 

 in the specific diagnosis are based on observation and measurements 

 of 20 mature specimens of each sex. 



Branchinecta campestris, new species 



Figures 1-5 



Specific diagnosis: Male: Length from front to end of cercopods 

 22.2 (15.9-28.5) mm. Ratio of length of head and thorax to that of 

 genital segments, abdomen, and cercopods 1:1.3 (1:1.13-1:1.5). 

 Antennule 2.3 (1.25-2.75) mm. long, length about 60 percent of 

 that of basal article of antenna, with 3 setae and 9 to 12 aesthetascs 

 at the tip. Antenna Particulate, 7.14 (5.25-9) mm. long. In 

 straight, uncontracted specimens, the antennae, bent backwards, 

 reach to thoracic segment 8, rarely to 7 or 9. Free part of proximal 

 article of antenna 4 (2.75-^4.75) mm. long, bearing an inconspicuous 

 apophysis on its median side near its proximal end, distal to which 

 is a file of from 7 to 15 small, conical sensory papillae 30-50 microns 

 high, each with 1 or 2 sensory bristles. Distal article of antenna 

 arcuate, its length across the arc 3.9 (2.75-4.75) mm.; nearly cylin- 



1 College of Fisheries, University of Washington. 



549 



